The U.S. Defense Advanced Research Projects Agency (DARPA) recently assigned Boeing the prime contract of Phase II for the Airborne Launch Assist Space Access (ALASA) program. The program aims to attach satellites to fighter planes in the first stage of their upward trajectory, replacing the expensive and complex space shuttles used to carry satellites into space. Phase II consists of 12 orbital test launches that will assess new technologies and equipment for the prototype aircraft, satellite housing, and monopropellant systems developed in Phase I.
The ever-growing waitlist for satellite launches prompted engineers to come up with a new plan of action. The slow rate of vertical space shuttle launches is caused by various factors: space stations are scarce, each launch can take months of preparation, and fixed launch stations are non-reconfigurable for satellites that require different directional orbits. Not to mention, launching satellites via space shuttle costs millions of dollars for fuel and preparation—averaging at $30,000 per pound of the payload.
Fighter planes, however, do not require complex vertical launch pads. Rather, they simply need runways, which are less expensive to prepare and a lot more accessible. Planes can easily be reconfigured on the runways and come right back down for another go with a different satellite. They also substantially save on fuel consumption and cost.
With these savings in time and resources, DARPA hopes to bring the price of a satellite launch down to $1 million per 100-lb payload, and produce an impressive turnaround of 24 hours per launch. Trials in Phase II will compare commercial-grade avionics and different technologies developed in Phase I in terms of their ability to bring down costs and facilitate satellite launch.
The Phase I prototype consists of a satellite housed in a launch vehicle and attached to a fighter plane. After taking off from its runway and reaching a high altitude, the satellite launch vehicle is released. The vehicle continues the second part of the upward trajectory, propelled by a newly designed monopropellant, until it reaches the level for low Earth orbit. It then releases the satellite.
The invention of a new, high-energy monopropellant in Phase I has the potential to reduce complexity and cost of the booster used for the second stage of the satellite trajectory. The monopropellant combines fuel and oxidizer, instead of using two separate fluids such as liquid hydrogen and liquid oxygen. This simplifies vessel design, and if successful, will likely affect the aircraft industry outside of satellite launching. Phase I also produced launch software, telemetry from other orbiting satellites, and automated flight-termination that will be tested in Phase II.